No because of the inability to run economic experiments. Thus conclusions drawn after the fact are not very dependable.
If one could start from the beginning and implement a different policy one may be able to drawn sound conclusions but as the case maybe they are only opinion buttressed by theory.
...a classic non-sequitur. Nor are economic experiments entirely impossible as you claim, especially on the micro level (doubt me? A guy just won the nobel prize for devising means of doing so a couple years ago). Returning to the point though, it simply does not follow from the _limitations_ of economic experimentation that ex post facto conclusions (read: experience itself) are unreliable. In fact, the innovative driving agent of economic growth is of such a nature that it can ONLY be known ex post, never ex ante - go read Schumpeter.
If one could start from the beginning and implement a different policy one may be able to drawn sound conclusions but as the case maybe they are only opinion buttressed by theory.
Tf one were to take the inanity you posted above to its logical extreme it could be said that we do NOT know communism killed the Soviet Union since there is no alternative can be tested from the beginning in 1917 for comparison. Using your reasoning we're just as right (or wrong depending on how you look at it) to dismiss the Soviet failure as a product of excess fluoride in their water, or perhaps something culturally with Russians, as something inherently wrong with communism. But that, of course, would be absurd and so is your bizarre insistence that we cannot intellectually evaluate the policy of protectionism in the early 19th century (unless, of course, that evaluation supports your desired outcome of vindicating the tariffs - and no credible study does).
If you see something fundamentally wrong about the throng of scholars who have concluded protectionism was a dismal failure, why not write it up and get yourself published? Simply dismissing results that you disagree with out of hand over a pretended and logically absurd quibble with the fact that they attempt to evaluate the policy itself won't cut it though.
It has been tried in myriad conditions, everything from American-style freedom to totalitarianism. It has never worked. At some point, a reasonable person would indicate that sufficient data exists with diverse enough initial conditions that they would declare it a failure.
Of course, requiring experimental data is a denial of other verification methodologies. People like test data because it's real but in cases where it's impossible to retrieve meaningful test data on an independent variable, inspection, demonstration, and analysis suffice to demonstrate the point. In this case, inspection and analysis suffice, since interjection of a third party cannot possibly come at zero cost.
Of course then, there is always a religious argument based on first principles: Any system controlled by a few power-elite subject to the evils of human nature is by definition rife with corruption. As you stated in a previous argument, it's beyond mortal control. You can curse God for making us that way (a practice I do not recommend), or admit that Hamilton was a man, and could not possibly have done what you ascribe him.